Familial chronic lymphocytic leukemia (CLL) families are being studied because they potentially provide a unique opportunity to study the development of CLL, a common neoplasm. We have studied the immunophenotypic profiles of patients with sporadic CLL and with familial CLL and found significant differences between the two groups. Furthermore, the association of prognosis with the cell surface proteint profile differs between familial and sporadic CLL. Primary effusion lymphoma (PEL) is a hematolymphoid neoplasm that presents in serous effusions without detectable tumor masses. The lymphoma cells express few markers making diagnosis difficult at times and quantitation of disease following therapy problematic. We have developed a flow cytometric assay that is useful in diagnosis of this lymphoma and in quantitating tumor cells in patient specimens. We have developed methods to quantitate antibody binding capacity in tumor cells present in low levels in lymph node, peripheral blood or bone marrow for patients under going antibody based therapy. This flow cytometric assay is performed in place of previous studies using radioactively labeled antibodies to measure tumor cell binding capacity in patients. The flow cytometric assay is more rapid, makes the use of radioactivity unnecessary and is performed on 100 micro liters of blood instead of 25mL. Furthermore, the data is more specific as levels of antibody binding are measured specifically in the tumor cells without the influence of other populations present in patient specimens. The data collected is also more precise and will be used to compare antibody binding to tumor cells to treatment response. Recent studies, using flow cytometry have demonstrated that endothelial cell precursors as well as mature endothelial cells can be detected in the circulation of patients with cancer and that the levels of these cells are significantly higher in patients with malignancy than normal controls. Furthermore, successful therapy for the malignant process may affect the number of activated circulating endothelial cells (CECs) in the peripheral blood. These data suggest that measurements of CECs and circulating endothelial cell precursors (CEPs) in the peripheral blood of cancer patients may be a used as a surrogate marker for the efficacy of anti-cancer strategies, particularly those that target tumor vasculature. We have developed methodology to measure levels of CECs and CEPs in the peripheral blood of patients with cancer or of patients undergoing surgical interventions, and to determine if these measurements can be used to follow response or disease progression across a variety of histologies and treatments. The utility of flow cytometric analysis in leukemia and lymphoma gained acceptance in the late 1980s. Since that time there has been growing concern among practitioners in the field of clinical flow cytometry about inconsistent practices as well as deficiencies in standardization and validation and its possible impact on patient care. To address this issue a group of U.S. and Canadian hematopathologists, hematologists and laboratory scientists met in Bethesda, MD from November 16-17, 1995 to develop the U.S.-Canadian Consensus Recommendations on the Immunophenotypic Analysis of Hematologic Neoplasia by Flow Cytometry. The consensus document produced provided guidance on standardization and validation of laboratory procedures, data analysis and interpretation and data reporting. Guidelines were also provided on medical indications for testing. Although consensus could not be reached at that time on the number or combination of antibodies utilized in flow cytometric evaluation of leukemia or lymphoma, strategies were provided for the selection of antibodies and lists of markers useful in identification of acute leukemias and lymphoproliferative processes were provided. Recently there was growing recognition of the need to set standards of training and education for practitioners in the field of flow cytometry, including technologists, interpreters and laboratory directors. It was also realized that the previous guidelines on medical indications for flow cytometric testing were no longer practical and that new guidelines on medical indications for flow cytometric analysis that are based upon clinical signs and symptoms suggestive of hematolymphoid neoplasia are needed in the field. Similarly, guidelines on antibody panels recommended for patients presenting with specific signs and symptoms are desirable. To address these issues the Flow Cytometry Unit, CCR, NCI, NIH organized the 2006 Bethesda International Consensus Conference on Flow Cytometric Immunophenotyping of Hematolymphoid Neoplasia was held from July 14-15, 20006 in Bethesda, MD. During this conference the important issues and goals were identified and a structure defined to achieve the identified goals. The final consensus recommendations on training, medical indications and antibody panels generated by this process were published in September 2007. The Flow Cytometry Unit, CCR, NCI, NIH has been instrumental in producing the regulatory document on flow cytometric immunophenotyping of lymphoma and leukemia, Clinical and Laboratory Standards Institute. Clinical Flow Cytometric Analysis of Neoplastic Hematolymphoid Cells; Approved Guideline-Second Edition. CLSI document H43-A2 . This guideline will be used as the gold standard when laboratories performing flow cytometric analysis of hematolymphoid malignancies in the United States are inspected by CLIA/CAP. It provides detailed technical guidelines for laboratory procedures involved in flow cytometric testing of hematolymphoid neoplasia. The Flow Cytometry Unit, CCR, NCI, NIH is currently participating in an international effort to develop guidelines for flow cytometric immunophenotyping of cerebral spinal fluid (CSF) in patients with hematolymphoid neoplasia